Paper moving schemes appearing in the art are numerous and include such devices as vacuum belts, vacuum trays, wave generators, large diameter rollers, soft high friction rollers, hard high friction rollers, and leading edge pullers. Means of moving, turning, or transporting said devices include chains, belts, blowers, etc. driven by a prime mover such as a motor.
In recirculating document feed devices, a document is passed through a processing station and then recirculated so that it passes through the processing station again. The cycle can be repeated any number of times until the desired number of processing steps have been completed. Recirculating document feed devices ordinarily use paper moving schemes involving gears and belts, etc. such as described above and as illustrated in U.S. Pat. No. 3,661,383. Such systems are subject to difficult document retrieval should a jam occur, they are costly relative to the invention to be described herein, and are difficult to adjust and maintain.
The instant invention involves a configuration in which it is possible to drive an entire system of paper moving devices by providing only one set of driven rolls directly connected to a prime mover and using frictional contact between those rolls and additional sets of freely rotating rollers to obtain document recirculation. The freely rotating rollers are positioned in a pivoting frame which opens to expose the document feed path to provide for ease of document retrieval, ease of mechanism adjustment, ease of maintenance and easy book copying. This arrangement provides a reliable low-cost drive which is quiet and safe because of its freedom from belts, chains, or gears. This is also important from a safety viewpoint since recirculating document feed devices are in an area of user access.
An additional advantage of the invention is the ability to bias the side of a moving document against a side reference edge with a controlled force so as not to crumple the edge of the document by making use of the principles described in U.S. Pat. No. 4,179,117. In an especially innovative and advantageous design, the invention incorporates a large freely rotating roller which forms a part of two roll nips in two different document feed paths and thus creates unusual problems in document side edge referencing in both paths. The invention herein solves that problem.
Additionally, the beam strength of documents when driven around the substantially 180.degree. bends of a recirculating document feed path creates slippage in roll nips and therefore unusual problems in maintaining alignment of the document against the side reference edge. Moreover, a document in two roll nips may be pulled through one nip by the other, again creating an unusual aligning problem. The invention herein provides a method for solving these problems.